Field of the Invention
The present invention relates to a hollow drive shaft for a vehicle and a manufacturing method thereof. More particularly, the invention relates to a hollow drive shaft for a vehicle and a manufacturing method thereof, which are intended to improve durability by enhancing physical properties without an increase in size.
Description of Related Art
Generally, a vehicle is equipped with a drive shaft to transmit power of an engine from a transaxle to left and right wheels of the vehicle, the transaxle being driven by power shift from a transmission.
The drive shaft is configured to be connected between a fixed center type constant velocity joint coupled to the left and right wheels and a slidable constant velocity joint coupled to the transaxle, thus transmitting power from the transaxle to the left and right wheels of the vehicle and thereby allowing the vehicle to be driven.
FIG. 1 is a sectional view schematically showing a conventional hollow drive shaft for a vehicle.
As shown in FIG. 1, the conventional hollow drive shaft includes a hollow shaft 1 that is provided on a central region thereof and has a hollow portion 4 extending in a direction of a rotation axis, and first and second stems 2 and 3 that are welded to both sides of the hollow shaft 1, respectively.
The conventional hollow drive shaft is made by joining the hollow shaft 1 at the central region to the stems 2 and 3 on both sides through a friction welding method in which parts (i.e. the hollow shaft and the first and second stems) are welded with pressure using frictional heat generated during the relative rotation of the welded parts.
Such a hollow drive shaft is higher in rigidity and strength compared to a solid drive shaft simply having a solid portion without having a hollow portion at the central region, thus leading to an increase in natural frequency. Consequently, the hollow drive shaft advantageously permits a damper to be eliminated, in addition to reducing a weight.
The damper is sensitive to temperature change and is deteriorated in performance for several reasons, such as rubber curing, over time. Thus, in the conventional hollow drive shaft, the elimination of the damper may cause several problems.
Meanwhile, an internal-combustion-engine vehicle performs forward movement rather than rearward movement and does not perform regenerative braking, so that the drive shaft is mainly driven under a unidirectional-movement condition in which torsion torque is applied in the forward movement direction of the vehicle. In contrast, in an eco-friendly vehicle performing the regenerative braking, such as a hybrid vehicle or an electric vehicle, the drive shaft is driven under a bidirectional-movement condition in which the torsion torque is applied in the forward movement direction of the vehicle at the time of the travel but is applied in the rearward movement direction of the vehicle at the time of the regenerative braking.
Therefore, if the hollow drive shaft, which does not consider the bidirectional-movement condition required for the eco-friendly vehicle, is mounted to the eco-friendly vehicle, durability is poor in the bidirectional movement and thereby the drive shaft may be undesirably damaged.
In order to solve the problem where such a drive shaft is damaged, a method of increasing the size of the drive shaft has been conventionally proposed. However, this may lead to an increase in diameter of the drive shaft, so that it is disadvantageous in terms of a layout.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.